Many people require more than one pair of corrective eyeglasses, depending on the circumstances they find themselves in. For example, many middle aged people are far-sighted. This means that they have little difficulty seeing objects at a distance, but have considerable difficulty seeing objects up close. These individuals have difficulty seeing print in a book clearly enough to read, so they need some sort of corrective lenses or magnifying glass in order to read. When such an individual is outside in the sun and wearing sunglasses, a practical problem arises if that individual wishes to read a book: he or she must purchase a pair of prescription sunglasses or endure the sun without the benefit of sunglasses. This practical problem is experienced by people needing prescription glasses for other purposes as well, such as myopia. The purchase of a second pair of prescription glasses is expensive and involves the further practical problem of carrying around an additional pair of prescription lenses (i.e., the prescription sunglasses). The present invention addresses this problem by providing a means for converting a pair of spectacles, such as sunglasses, safety glasses, sports goggles or eyeglasses, into corrective and/or magnifying lenses, or for altering the corrective and/or magnifying properties of a pair of eyeglasses.
Many attempts have been made at simplifying the spectacle needs of people who wear corrective lenses, whether they wear corrective lenses at all times or only on occasion for specific tasks. For example, one attempt to solve the problem of having to purchase and carry two pairs of prescription eyewear at the same time is to wear contact lenses. The contact lenses can be prescription lenses and thus the wearer need carry only a single pair of tinted eyewear for use as sunglasses or can wear safety glasses with contacts. However, many people have difficulty wearing contact lenses, and many of those who do wear contact lenses find them irritating at times, particularly in bright sunlight and windy weather. Additionally, many people find that contact lenses require substantial efforts to insert, remove, and clean.
Another alternative to carrying two or more pairs of spectacles has been to use a pair of prescription eyeglasses that are tinted in such a way that there is a minor tint when the ambient light is relatively low, and a more severe tint as the ambient light becomes brighter. This approach is disadvantageous, because such eyeglasses are relatively expensive and the tint of the lenses may change at times when it is not desirable for it to change.
Yet another attempt to resolve the need for two pairs of corrective eyewear is to use "clip-on" or "snap-in" tinted lenses in connection with a pair of clear prescription eyeglasses. Clip-on lenses may be attached to a pair of eyeglasses by a clip, typically located at the center of the clip-on lenses. The clip may attach over the nosepiece of the eyeglasses. Sometimes the clip snaps over the sides of each of a pair of separate lenses formed to the shape of specific eyeglasses for which they are provided. In another variation, a tinted lens is snapped into a circumferential groove inboard of the clear lens. And in yet another attempt to solve the problem, clear prescription lenses are hung, hinged or otherwise detachably mounted inboard of a pair of conventional sunglass lenses. Typically, some additional structure, is added to the sunglass frames for holding a prescription lens or pair of lenses behind the sunglass lenses. In one species, the frames themselves are modified with threads to receive a "screwed-in" prescription lens for each lens of the sunglasses.
Despite these various efforts to develop a functional and comfortable "clip-on" lens, clip-on lenses can be disadvantageous because they result in less than desirable optics, typically through an inability to control the spacing and angular relationship between the sunglass lens and its clear lens with any precision or degree of stability, are heavy and tend to cause the eyeglasses to slip, and because they are often cosmetically unattractive.
Additional efforts have been made to resolve the issues presented when more than a single pair of spectacles is required for particular circumstances, or as circumstances change. Recently, 3M Company has provided on die cut sheets small "half-lens" shaped magnifiers cut from relatively flat vinyl stock and which employ a molded in Fresnel type grating for an optical magnification effect. These 3M lenses suffer from optical aberrations and poor performance, especially when adhered to the panes of a pair of spectacles. In addition, the magnifying power of the Fresnel material does not adapt well to bending and is not readily adaptable to prescription configurations.
Efforts have also been made to resolve the problems associated with adapting a pair of spectacles to correct a person's vision. For example, U.S. Pat. No. 3,628,854 of Jampolsky, dated Dec. 21, 1971, for "FLEXIBLE FRESNEL REFRACTING MEMBRANE ADHERED TO OPHTHALMIC LENS" (hereinafter "Jampolsky '854 patent"), and U.S. Pat. No. 4,079,160 to Philipson, dated Mar. 14, 1978 and entitled "ABRASION-RESISTANT OPTICAL ELEMENT" (hereinafter "Philipson '160 patent") attempt to address these issues. Whereas the first of these references recognized the fact that certain polymers possess autogenous adhesive properties which enable membranes thereof to be stuck by mere finger pressure to the surface of an optical lens, it did not contemplate lenses which are injection molded from self-adherent polymeric material and which are characterized by truly optical corrective or enlargement properties, so that a magnifying or reader-type set of eyeglasses, or a set of eyeglasses embodying corrective lenses, could be produced by the simple pressed-on adherence of the lens to the surface of a sunglass lens or other simple plano lens having no correction itself, to provide simply and expediently, a set of "reader" glasses or glasses comprising corrective lens elements in a most facile and economic manner. The polymeric membrane described in the Jampolsky '854 patent is of vinyl butyrate, of which thicknesses in excess of one-sixteenth of an inch are not recommended, and the most significant disclosure of this patent is clearly the presence of a Fresnel refracting surface which refracts light rays transmitted through an ophthalmic lens and the membrane of Jampolsky to the eye, in a manner enabling diagnosis and treatment of a disorder of the eye.
The Philipson '160 patent, although employing an aliphatic polyurethane, among many different polymeric substrates which are disclosed as being utilizable for the production of a hard abrasion-resistant coating on optical surfaces, as present in a pair of eyeglasses or sunglasses, did not contemplate or suggest the production of a press-on lens having truly optical or magnification characteristics from such type of polymer or any other. The Philipson patent thus relates to a hard protective lens coating.
In addition to the foregoing, U.S. Pat. No. 3,033,359 to Mercer discloses the employment of SARAN.TM. for temporarily attaching shields to optical lenses by electrostatic attraction; U.S. Pat. No. 4,898,459 to Eriksson discloses releasably attaching opaque films to reading spectacles; U.S. Pat. No. 2,248,638 to Merton discloses sheet material having prismatic surfaces; U.S. Pat No. 2,511,329 to Craig discloses a lens shield adhered to a lens by adhesive on one side of a thin flexible transparent sheet material (which is a drawback because adhesive affects the refraction of light penetrating the lens and lens shield); U.S. Pat. No. 2,884,833 to Pohl discloses an optical system for viewing pictures; U.S. Pat. No. 3,004,470 to Ruhle discloses a multiple focal lens; U.S. Pat. No. 3,203,306 to Lefferts discloses an optical ray concentrator; French Patent 369,993 relates to protective goggles; published British Specification 717,775 relates to colored viewers with areas of different colors so that an object viewed appears to be colored; and Swiss Patent 207,794 relates to a protective screen for eyeglasses and the like.
There is a need for a simple, inexpensive corrective lens that may be used in connection with a pair of spectacles to provide a simple magnified or corrective pair of sunglasses, or to modify the correction of a pair of eyeglasses, that can be used comfortably and effectively for sustained periods of time. Thus, there is a need to adapt non-corrective sunglasses for use as corrective sunglasses, and to adapt corrective eyeglasses as needed for specific tasks, without the above noted disadvantages. The present invention provides these and other advantages.